OSCM II - Oxoid

OSCM II
Oxoid Salmonella Chromogenic Medium II (OSCM II)
THE FIRST IN A NEW CLASS OF MEDIA INCORPORATING INHIBIGEN
TECHNOLOGY*. OSCM II – FOR THE ISOLATION AND PRESUMPTIVE
IDENTIFICATION OF SALMONELLA SPECIES.
NOVEL
The first culture medium to incorporate novel Inhibigen
technology for targeted selectivity.
SELECTIVE
Use of Oxoid proprietary Inhibigen technology means improved
recovery of Salmonella due to reduced background flora.
EASY TO READ
Use of carefully selected chromogens results in brightly coloured
colonies for easy identification of Salmonella.
COST EFFECTIVE
Increased selectivity screens out negative samples more effectively,
reducing the need for further testing.
EVERYTHING YOU NEED
Oxoid provides all the culture media and reagents you need for
isolation and identification of Salmonella.
*Patent pending.
Chromogenic Media

INTENDED USE
Oxoid Salmonella Chromogenic Medium Mark II (OSCM II) is for the
presumptive identification and differentiation of Salmonella species.
SUMMARY
OSCM II is a unique medium that combines the benefits of chromogenic media
with new Inhibigen technology to reduce time to results over standard culture
methods. Inhibigens are a new class of agent, developed by Oxoid, which can
be used to target specific groups of organisms and prevent them from growing.
In OSCM II, a specifically tailored Inhibigen is combined with other selective
agents and the growth of non-target micro-organisms is significantly reduced.
Carefully selected chromogens give excellent differentiation making it even easier
to identify Salmonella and reduce the number of false positive colonies requiring
confirmation.
PRINCIPLES
An Inhibigen compound comprises of two components combined together
by a bond that can only be cleaved by specific enzymes. When bound, the
inhibitor component is not toxic and therefore can exist in a medium without
harming micro-organisms. Once inside the cell, the bond will be cleaved if the
target enzyme is present. When the bond is cleaved, the inhibitor molecule is
released, disrupting cell replication, resulting in targeted inhibition. As cells die
and lyse, free inhibitor is released but cannot be taken up by other cells. The
Inhibigen in OSCM II is used to specifically inhibit growth of Escherichia coli.
Differentiation of Salmonella from any other organisms that are able grow on
OSCM II is achieved through the inclusion of two chromogens in the medium:
magenta-caprylate and X-ß-glucopyranoside. Caprylate esterase is an enzyme
present in all samonellae and some species of Klebsiella, Enterobacter and
Proteus1 . Organisms possessing caprylate esterase cleave the chromogen to
release an insoluble purple chromophore. As the cells grow the chromophore
builds up and produces a purple-coloured colony. Some Enterobacteriaceae
including Klebsiella and Enterobacter, but not Salmonella, possess ßglucosidase,
which means that they are capable of taking up and cleaving X-ßglucopyranoside2
. If these organisms grow they will form blue or dark blue
colonies, which make them easy to differentiate from purple Salmonella colonies
even if they are esterase positive.
Novobiocin and cefsulodin inhibit the growth of other competing flora such as
Proteus spp. and pseudomonads.
PRODUCT SIZE ORDER CODE
OSCM II Base 108g (2 litres) CM1092E
OSCM II Base 500g CM1092B
Salmonella Selective Supplement 10 vials (each for 500ml) SR0194E
OSCM II Plates 10 plates PO1118A/
PO5098A*
* Check codes and availability with your local Oxoid supplier.
FORMULA
PER LITRE
Salmonella Growth Mix/Nutrient mix 14.0g
Chromogenic Mix 25.0g
Agar 15.0g
Novobiocin 5.0mg
Cefsulodin 12.0mg
Final pH 7.3 ± 0.1 at 25ºC.
500g of OSCM II Base will make 9.2 litres. Each litre of medium requires the
addition of 2 vials of Salmonella Selective Supplement. Each box of supplement
contains 10 vials.
OSCM II
REFERENCES 1. Cooke. V.M. et al. A Novel Chromogenic Ester Agar Medium for Detection of Salmonellae. Appl. Environ. Microbiol. Feb 1999 p. 807-812, Vol. 65, No. 2. 2. Garrity, G., Brenner, D.J., Krieg, N.R.,
Staley, J.R. (Eds.) Bergey’s Manual of Systematic Bacteriology. Vol 2, Part B. 2nd ed., 2005. US, Springer. 3. ISO 6579:2002 Microbiology of food and animal feeding stuffs – Horizontal method for the detection of
Salmonella spp.
DEDICATED TO MICROBIOLOGY
DIRECTIONS
Suspend 27 grams of OSCM II Base in 500ml of distilled water. Add the contents
of 1 vial of Salmonella Selective Supplement, re-suspended as directed. Mix well
and sterilise by bringing to the boil with frequent agitation. Cool to around 50°C,
mix well and pour into sterile Petri dishes.
NOTE: It is critical that the selective supplement is added prior to heating. When
preparing volumes greater than 1 litre, contact Oxoid Technical Support for directions.
METHOD OF USE
OSCM II can be used for food, environmental and clinical samples, following a
variety of enrichment procedures i.e. ISO, NMKL, FDA, HPA, etc.
The following method is a summary of ISO 6579:20023 where a 2nd medium of
choice may be used alongside XLD Agar:
1. Add 25g of food sample to 225ml of Buffered Peptone Water and stomach for
a minimum of 30 seconds to mix the sample.
2. Incubate the broth at 37ºC for 18 h ± 2 h.
3. Gently agitate the bag then, using a pipette, inoculate 1ml into 10ml of
MKTTn Broth and 0.1ml into 10 ml of RVS Broth. Incubate MKTTn broth at
37ºC for 24 h ± 3 h and RVS broth at 41.5ºC for 24 h ± 3 h.
4. Using a microbiological loop sub-culture each broth onto one XLD Agar plate
and one OSCM II plate to give a total of 4 plates.
5. Incubate the plates at 37ºC for 24 h ± 3 h.
6. Confirm presumptive red colonies with black centres from XLD and purple
colonies from OSCM II as Salmonella species by appropriate biochemical and
serological methods. Refer to ISO 6579:20023 .
The following Oxoid products may be useful for confirmation: Nutrient Agar
CM0003, TSI Agar CM0277, Urea Agar CM0053 & SR0020K, Lysine
Decarboxylase Medium CM0403, Methyl-Red Voges-Proskauer (MRVP) Medium
CM0043, Tryptone Soya Broth CM0129, Agglutinating Sera (see Oxoid product
list for codes), Oxoid Salmonella Latex Test Kit DR1108A, Microbact (see Oxoid
product list for codes), O.B.I.S. Salmonella ID0570M.
APPEARANCE, STORAGE & STABILITY
Dehydrated Agar Base: white/cream coloured, free-flowing powder. Selective
Supplement: white, freeze-dried pellet. Prepared Medium: white/cream coloured
opaque gel.
OSCM II Base should be stored tightly capped in the original container at 10-30ºC.
Salmonella Selective Supplement should be stored in the dark at 2-8ºC. When
stored as directed, the un-opened products will remain stable until the expiry
date printed on the packaging. Store in-house prepared medium in the dark at
2-8ºC for a validated period. OSCM II ready-to-use plates should be stored as
indicated on the packaging.
LIMITATIONS AND PRECAUTIONS
With all Salmonella media there are a small number of atypical strains that may
give a weak reaction or fail to grow.
OSCM II Base and Salmonella Selective Supplements are for laboratory use only.
Do not use OSCM II Base and Supplement beyond stated expiry dates, or if the
products show any signs of deterioration. Material Safety Data Sheets and QC
certificates are available on the Oxoid website www.oxoid.com
QUALITY CONTROL TESTING
ORGANISM CULTI-LOOPS ® TYPICAL COLONY
ORDER CODE APPEARANCE
Salmonella Typhimurium
ATCC
C6000L
Good growth
® 14028 † Purple colony
Klebsiella pneumoniae
ATCC
C7037L
Good growth
® 13883 † Blue colony
Enterococcus faecalis
ATCC
C7030L Inhibited
® 29212 †
Escherichia coli
ATCC
C7050L Inhibited
® 25922 †
www.oxoid.com
Oxoid, Wade Road, Basingstoke, Hants, RG24 8PW, UK. Tel: +44 (0) 1256 841144 Fax: +44 (0) 1256 463388 Email: oxoid.food@thermofisher.com
†The ATCC Licensed Derivative Emblem ® , the ATCC Licensed Derivative word mark ® , and the ATCC catalog marks are trademarks of ATCC.
Oxoid Ltd is licensed to use these trademarks and sell products derived from ATCC ® cultures.
© 2007, Oxoid Ltd.; copyrights to photographs held separately; contact Oxoid Ltd. for details. Photographs may not be extracted or reproduced in any way.
Folio No: 1090/07/07